A silver halide color photographic material (hereinafter sometimes referred to as a photographic material simply) generally has silver halide emulsion layers sensitive to three primary colors, i.e., red, green and blue. Color reproduction is achieved by the subtractive process by incorporating three kinds of color couplers in the emulsion layers. The color couplers are capable of forming dyes, each of which has a complementary color relationship to color to which the corresponding emulsion layer is sensitive. Color images which are obtained by photographically processing this photographic material generally comprise an azomethine dye or an indoaniline dye formed by a reaction of the oxidation product of an aromatic primary amine developing agent with the coupler.
The thus-obtained color images are not necessarily stable against light, humidity and temperature, and the discoloration of color images are liable to occur when exposed to light or stored under high humidity and high temperature conditions for a long period of time, leading to the degradation of color images.
These kinds of discolorations are fatal to recording materials. Various countermeasures against these drawbacks are proposed, such as the development of couplers having a high stability of dye obtained, the usage of discoloration inhibitors and UV absorbing agents to prevent the degradation of images by ultraviolet rays.
The effect of discoloration inhibitors to prevent the degradation of images is great of the above measures. Specific examples of discoloration inhibitors which can be used include hydroquinones, hindered phenols, catechols, gallic acid esters, aminophenols, hindered amines, chromanols, indanes, and ether or ester derivatives obtained by silylating, acylating or alkylating the phenolic hydroxyl groups of the above compounds, in addition, metal complexes can also be used.
These compounds have effects as discoloration inhibitors of color images but are insufficient to meet the demands of users who have required high quality images. Moreover, some of them adversely affect photographic characteristics, such as they cause considerable extent of color stains in the white background area, they cause coloring of the unexposed area (hereinafter, referred to as fog), they cause hindrance of coloring of couplers, they react with the oxidation product of a developing agent at the time of color development to form dyes leading to a cause of color turbidity, and they alter the original hue obtained by the couplers. Further, these compounds sometimes cause insufficient dispersion, or generate crystallites after emulsion coating, therefore, they are not comprehensively effective as discoloration inhibitors for color photographic use.
Compounds having bisphenol structures are also known as image degradation inhibitors. These compounds, although effective as discoloration inhibitors, have problems such as they cause lowering of coloring when used in a large amount for the purpose of satisfying recent strong demands for high stability of color images, cause yellow stains in the white background area with the lapse of time, and react with the oxidation product of a developing agent at the time of development to form dyes resulting in a cause of color turbidity.